The core library is written in plain C#.

The Windows GUI is developed in WPF, i.e. a combination of C# and XAML. On top of our own controls, we use a number of open source projects we would like to thank for their excellent work:

We currently store data in a very simple database in XML.

The Excel GUI is developed by combining Visual Studio Tools for Office with ExcelDna, a great project whose author we are also very thankful to.